A Dye-Sensitized Solar Cell (DSSC) functions as an electrochemical cell. U.S. Pat. No. 4,927,721 entitled “Photo-Electrochemical Cell”, by M Gratzel et al discloses a typical DSSC. As illustrated in FIG. 1: a typical DSSC 10 comprises a substrate 1; a first electrode 2; a metal oxide layer 3; a functional dye layer 4; an electrolyte layer 5; a second electrode 6; and a second insulating layer 7.
The DSSC 10 generates charge by the direct absorption of visible light. Since most metal oxides absorb light predominantly in the ultra-violet region of the electromagnetic spectrum, the sensitiser (dye) 4 is absorbed onto the surface of the metal oxide layer 3 to extend the light absorption range of the metal oxide layer 3 into the visible light region.
In order to increase the amount of light that the metal oxide layer 3 can absorb, at least some portion of the metal oxide layer 3 is made porous, increasing the surface area of the metal oxide layer 3. This increased surface area can support an increased quantity of functional dye 4 resulting in increased light absorption and improving the energy conversion efficiency of the DSSC by more than 10%.
DSSC devices known in the art can be improved by fabricating the metal oxide layer as an array of micro-scale, high-density cells surrounded by barriers such as banks. In order to fabricate the banks, device fabrication techniques such as optical lithography, micro-embossing, optical interference lithography etc. can be employed because these techniques have become a key technology for mass production patterning techniques. Whilst these techniques allow for high-resolution patterning upon a substrate, tool alignment with previously defined structures upon the substrate is difficult. Accurate alignment is especially difficult in the case of large area, flexible substrates, due to the occurrence of warping, thermal expansion or shrinking of the substrate. Furthermore, in the case of roll-to-roll fabrication techniques, non-uniform distortions due to the necessary tensions applied to the substrate during transfer can cause further alignment difficulties.
One limitation to the realisation of mass produced DSSCs is therefore a lack of high resolution patterning techniques providing good alignment.